Gold enthrals terribly giving complete power over someone (12)
I believe the answer is:
stranglehold
'complete power over someone' is the definition.
(as in having someone in a stranglehold)
'gold enthrals terribly' is the wordplay.
'terribly' indicates an anagram.
'gold'+'enthrals'='goldenthrals'
'goldenthrals' is an anagram of 'STRANGLEHOLD'.
'giving' is the link.
(Other definitions for stranglehold that I've seen before include "exclusive control?" , "Inexorable grip" , "Complete control" , "Complete power over a situation" , "Star long held (anag) - complete power over a person" .)